Develop Reference

sending form data with javascript with XMLHttpRequest asynchronously

I am sending some form data with an XMLHttpRequest
let xhr = new XMLHttpRequest();
xhr.open("POST", url, true);
xhr.setRequestHeader("Content-Type", "application/json");
try {
let data = JSON.stringify(sendForm);
xhr.send(data);
alert(xhr.status);
}
catch (error) {
alert(error);
}
This works as it will go into this after the alert pops up in the browser
xhr.onreadystatechange = function () {
if (xhr.readyState === 4 && xhr.status === 200) {
location.href = 'thanks.html';
}
and data will be inserted into the database as expected. However, if I comment out the alert after the xhr.send(data); this code will no longer inserts data into the database or display the correct page, it just displays the js file. If I set a break point at xhr.send(data) when I step past it is when the js file is displayed.
Any thoughts as to why the data is being sent if I include the alert(xhr.status) step in the code but not when I comment it out? Also, any thoughts why the try{}catch{} is not catching the error? Thanks I am not very familiar with javascript right now.

Fetch XML without getting blocked (CORB)

For example I want to fetch https://www.w3schools.com/xml/simple.xml
to my website http://example.com.
This is the code
var xhr = new XMLHttpRequest();
xhr.open("GET", 'https://www.w3schools.com/xml/simple.xml', true);
xhr.onload = function () {
if (xhr.readyState === 4 && this.status === 200) {
console.log(this);
}
}
xhr.send();
I'm getting an empty response and a warning saying
Cross-Origin Read Blocking (CORB) blocked cross-origin response https://www.w3schools.com/xml/simple.xml with MIME type text/xml. See https://www.chromestatus.com/feature/5629709824032768 for more details.
Then I had been studying these CORB rules. Some developers are saying that it is not possible to get data from another origin.
But is it really the case?
In the project I'm working on, it is a public xml feed, and since the owner are updating the feed quite often - and I would like to have my website in sync with the feed - I assume it is not possible? Do I really have to create a xml file, and copy-paste the xml data and upload it to my server each time?
Or is there a way to fetch this data directly from the url somehow?

You could create a PHP script like this:
<?php
header("Content-type: text/xml");
echo file_get_contents('https://www.w3schools.com/xml/simple.xml');
?>
Call this simple.php and then amend your Javascript to call simple.php instead:
var xhr = new XMLHttpRequest();
xhr.open("GET", 'simple.php', true);
xhr.onload = function () {
if (xhr.readyState === 4 && this.status === 200) {
console.log(this);
}
}
xhr.send();

Ajax Yelp API Call from Javascript

I'm trying to make a call to the Yelp API from JavaScript, but getting an error. Below is my code. I believe I will have to use Oauth, but I don't know where should I put it in the header.
function doAjax(){
var xhr = new XMLHttpRequest();
var url = "http://api.yelp.com/v2/searchterm=cream+puffs&location=chicago";
xhr.onreadystatechange = function(){
if(xhr.readyState == 4 && xhr.status == 200){
var some = JSON.parse(xhr.responseText);
}
}
xhr.open('GET', url, true);
xhr.send();
}

The problem is that you are trying to access a resource that is on a different domain from your application. In this case your application resides on http://fiddle.jshell.net and the resource is at http://api.yelp.com.
CORS is one way to get around this, see here:
http://en.wikipedia.org/wiki/Cross-origin_resource_sharing

HTTP Status Code from URL in Javascript

I'm trying to find a function that return HTTP Status Code from an URL, and then "make something" based on the returned statuses (404, 416, 200 etc...)
Can someone help me? I've tried the other functions posted here on StackOverflow but anyone was usefull for my purpose.
I need to integrate this function inside my PlayFramework web-app.
Thanks a lot

Can you try the following ..?
function getStatus(url) {
var request = new XMLHttpRequest();
request.onreadystatechange = function() {
if (request.readyState === 4){
request.status;//this contains the status code
}
};
request.open("GET", url , true);
request.send(null);
}

Using javascript to submit a post request to a server

I am working on a web crawler that can integrate with our partner portals and submit post requests to make bid changes.
The trouble is that the crawler runs in an environment which cannot execute jQuery, only native Javascript.
I have determined that the following AJAX code successfully sends the post request:
$.ajax({
type: "POST",
url: "http://acp.example.com/campaigns/122828",
data: "data-string"
});
Is there a way to translate the above statement into native javascript so that the crawler can execute it?
UPDATE
When executing hex494D49's native Javascript below, I am receiving a "NetworkError: 404 Not Found - http://acp.fyber.com/campaigns/122828" message.
However, when I execute the original AJAX code in firebug, it successfully sends the POST request.
Any idea why the same url would return a 404 error using native Javascript as opposed to AJAX?
Thanks

Sending AJAX request using POST method
var xhr = new XMLHttpRequest();
var url = "url";
var data = "email=hey#mail.com&password=101010";
xhr.open("POST", url, true);
xhr.setRequestHeader("Content-type","application/x-www-form-urlencoded");
xhr.onreadystatechange = function () {
if (xhr.readyState == 4 && xhr.status == 200) {
// do something with response
console.log(xhr.responseText);
}
};
xhr.send(data);
Sending AJAX request using GET method
xhr = new XMLHttpRequest();
var url = "url?email=hey#mail.com&password=101010";
xhr.open("GET", url, true);
xhr.onreadystatechange = function () {
if (xhr.readyState == 4 && xhr.status == 200) {
// do something with response
console.log(xhr.responseText);
}
}
xhr.send();
To avoid unexpected requests to the server, it's a good practice to use encodeURIComponent() method on any user-entered parameters that will be passed as part of a URI.